Flame retardant materials

ABSTRACT

A rubber or plastics composition contains a flame-retarding agent containing calcium and borate radicals. A preferred agent is a hydrated mineral such as colemanite. The agent may be used in combination with a filler such as calcium carbonate and alumina trihydrate.

United Stat Pitts et al.

' Aug. 7, 1972 FLAME RETARDANT MATERIALS Inventors: Frank Pitts, Kersal; Michael Hilton Clubley, Bolton, both of England Assignee: Magnesium Elektron Limited,

Swinton, Manchester, England Filed: July 30, 1973 Appl. No.: 383,544

Foreign Application Priority Data Great Britain 36726/72 US. Cl 260/2.5 AJ, 106/15 FP,117/161 R, 117/161 UH, 117/161 UZ, 117/161 KP, 117/161 K, 260/45.7 R

int. Cl. C08c 17/08 Field of Search 260/45.7 R, 251A]; 106/15 FP; 117/161 R [451 Febiill, 1975 [56] References Cited UNITED STATES PATENTS 3,202,570 8/1965 Videen 162/159 3,367,863 2/1968 Cooper et al. 106/15 FP Primary Examiner-Melvyn l. Marquis Attorney, Agent, or Firm-Karl W. Flocks [57 ABSTRACT 10 Claims, N0 Drawings FLAME RETARDANT MATERIALS This invention relates to rubber or plastics material containing flame-retardant agents.

In the manufacture of foamed rubber or plastics material it is customary to incorporate fillers to improve the mechanical properties of the material and also to reduce its cost. Examples of fillers of this kind are calcium carbonate and china clay. One major industrial application of such materials is in the backing of carpets with foamed rubber or in producing a separate foamed rubber under-lay for use under carpets.

One serious disadvantage of such materials is that they are inflammable and once burning commences the flames spread very rapidly. It is accordingly known to incorporate flame retardants in the material and in some cases halogen-containing products, such as penta-bromo-toluene or chlorinated paraffins, have been compounded with a conventional filler such as calcium carbonate or china clay. It is also known to use zinc borate or antimony oxide in a similar manner. An alternative method of producing a foam with improved flame retardant properties is to replace the conventional filler, which itself has no significant flame retardant properties, with another filler which not only provides adequate mechanical properties but which also imparts flame retardancy. For example, it is known to use trihydrate of alumina in this way. Although foamed rubber compounded from rubber and tri-hydrate of alumina is substantially cheaper for a given degree of flame retardancy than that compounded from rubber, calcium carbonate (or china clay) and one of the flame retardant additives referred to above (e.g. pentabromotoluene) it is still very costly in comparison with ordinary (non flame-retardant) foamed rubber using only calcium carbonate since this may be produced by comminution of naturally occurring limestone, a very cheap and abundantly available mineral.

According to one aspect of the present invention there is provided a rubber or plastics material containing a flame-retarding agent comprising an inorganic compound containing calcium and borate radicals. The compound is preferably a natural mineral comprising a hydrated salt.

A preferred flame-retarding agent is the naturally oc curring mineral Colemanite, which is a hydrated calcium borate, Ca B O .5H O. When comminuted and incorporated into the material Colemanite also acts as a mechanical filler. Colemanite is a cheap, readily available mineral. Other minerals which may be used include ulexite, Na O.CaO 5 B 16 H 0 and pandermite, 4 CaO.5B O .7H O.

The material may be foamed in conventional manner (e.g. foamed polyurethane) or solid (i.e., unfoamed), e.g. solid rubber.

The flame-retarding agents of the invention may be used either alone or in conjunction with other fillers and flame retardants such as calcium carbonate or trihydrate of alumina. A composition may be made from rubber Colemanite and penta-bromo-toluene in which casc the material will be more resistant to spread of flame than if it were made from rubber and the same quantity of Colemanite only. The penta'bromo-toluene may be replaced by chlorinated paraffins or other halogen-containing flame retardant organic additives and the material will again have more resistance to spread a. t I I EXAMPLE The method used for preparing a foamed rubber and the methods of testing are as follows:

PREPARATION OF FOAMED RUBBER All the foamed rubbers were made using reagents and methods of preparation supplied by Revertex Co. Ltd. The basic formulation is shown below:

Parts by weight Rubber Latex Revinex 34 D40 178.6

Registered Trade Mark) Cure agent+ Tetrasodium Pyrophosphate l (T.S.P.P.)

Forming agent+ 8 Thickner solution Water Filler This represents I00 parts of latex on a dry basis. All weights are on this basis. These are proprietary products. It is known that the cure agent contains a Zinc compound. the foaming agent is a potassium oleate solution and the thickener solution comprises methyl cellulose or a similar cellulose derivative.

The cure is stirred slowly into the latex followed by the T.S.P.P. The filler is added and the rate of stirring is controlled to keep aeration to a minimum. When fully dispersed, the foaming agent and thickener solution are added. After addition of enough water to produce an acceptable viscosity, the mixture is transferred to the bowl of a household food mixer with a wire whisk, such as a Kenwood Chef mixer and whisked with the wire attachment until the required wet foam density is achieved. This is readily determined by weighing a known volume.

When the required density is reached, the mixer speed is reduced to a minimum for 5 minutes to refine the foam, i.e., to render the bubble size small and uniform. The foam is spread on hessian or a glass plate between machined side plates to control the thickness, skinned under infra red lamps for three minutes and then dried and cured in a hot air oven for 20 minutes at 140 C. Foams are allowed to condition for at least 48 hours at room temperature prior to testing.

TESTING OF FOAMED RUBBERS Flammability Tests The test used is the oxygen index determination given in ASTM (D 2863-). The oxygen index is the minimum concentration of oxygen, expressed as volume per cent, in a mixture of oxygen and nitrogen which will support combustion. Physical Tests Physical testing of the foamed rubbers includes com pression set, thickness and compression recovery tests as follows:

Compression Set Compression set is the permanent deformation resulting from the application of compressive stress. Test pieces are cut from the foam and their thickness measured. The pieces are then compressed to The above example relates to the use of Colemanite as a flame retardant filler in foamed rubbers, but the invention is not limited to such rubber products; it is 'equally applicable to compositions either of a foamed half this thickness using accurately machined washers 5 or solid (no -foa ed) at m d f synthetic to maintain the calculated gap between flat, clamped polymers such as polyvinyl chloride, polyolefines, polyplates. The apparatus is then placed in a hot air oven h e polyesters or polyester/polyamide systems at 70C for 22 hours. After this time the assembly is red to lid bb products,

moved from the Oven and iiie test pieces removed- The The compositions of the invention are suitable for thickness is again measured after 30 minutes recovery use i many d a where flameqesismnce i neces.

at l temperaturesary or desirable, particularly in carpets and upholstery Thickness and Compression Recovery Thickness of materials for use in buildings and in vehicles.

the foams under load is measured using a W.I.R.A. Carpet Thickness Gauge and a method based on 8.5. 4098: we Cla'm:

1967 which relates to carpets. The apparatus has a flat 5 A compos mon Consisting of rubber and circular presser foot with an area of 1 square inch and a f l agent. Comprising an mcrgamc .com-

under normal conditions exerts a pressure of 0.25 pound comauimg f radicals m an [bf/m It is at this pressure that the base thickness of amount siifficlent impart significant flame retard the foam is measured. By applications of weights, the ency to said Composition I thickness of the foam at 0.75, 3, 6, 9 and I2 lbf/in can A composition according to Ciaim m which [he b measured inorganic compound is a natural mineral comprising a The procedure is to increase the pressure stepwise to hydrated Saii- I the maximum and then reduce it in similar steps until A Composiiion according Ciaim in which the it is 0.25 lbflin A graph of the thickness against presinorganic Compound is coiemimiiesure is the pl tt d, 4. A composition according to claim 2, in which the Thickness and compression recoveries can be calcuinorganic Compound is Selected from Uiexiie and P lated as follows: dermite.

If; 5. A composition according to claim 1, in which said 1 is the original thickness at 0.25 lbf/i pressure composition also contains a flame-retarding agent in I is the compressed thickness at 12 lbf/in pressure 3 addition {0 Said Compoundis the recovered thickness at 0.25 Ibf/in pressure A Composition according to Ciaim 5, in Whifih Said after loading to 12 lbf/in pressure additional flame-retarding agent is selected from tri- The percentage thickness on recovery is: hy rate of winagnd organic flame-retardant compounds containing bromine or chlorine. 7. A composition according to claim 1, which conand the percentage compression recovery is: tains calcium carbonate as a filler.

8. A composition according to claim 1, which is untc/l" [c X 100 foamed and in which the average grain diameter of said The results obtained are shown in the table below inorganic compound is about 1 micron.

TABLE FILLER AND LOADING OXY- COMP. COMP. THICKNESS Parts by weight per 100 parts lh l X SET REECOV- RECOVERY dry rubber latex '70 I7? 7,. COLEMAN- TRIDY- CALCIUM ITE DRATE OF CAR- ALUMINA BONATE I 29 5 94 95 I00 5O 26 9 9I 75 75 25 9 82 91 50 100 25 9 95 75 75 31 1O 90 95 30 ll 92 96 150 23 7 88 93 It may be seen from the above results that foamed 9. A composition according to claim I, which is rubber products containing Colemanite as filler are foamed and in which the inorganic compound has an substantially equal in mechanical and flame retardant average grain diameter from 3 to 150 microns.

properties to those containing an equal weight of tril0. Carpet and upholstery material, comprising a hydrate of alumina as filler. It also demonstrates that 65 composition as claimed in claim 1 adhered to the un- Colemanite may be used alone as the flame retardant filler or in admixture with calcium carbonate or trihydrate of alumina.

dersurface of said carpet and upholstery material.

Notice of Adverse Decision in Interference In Interference No. 99,548, involving Patent No. 3,865,760, F. Pitts and M. H. Olubley, FLAME RETARDANT MATERIALS, final judgment adverse to the patentees was rendered Apr. 10, 1978, as to claims 1-4 and 7-10.

[Ofiicial Gazette August 8, 1.978.] 

1. A COMPOSITION CONSISTING ESSENTIALLY OF RUBBER AND A FLAME-RETARDING AGENT COMPRISING AN INORGANIC COMPOUND CONTAINING CALCIUM AND BORATE RADICALS IN AN AMOUNT SUFFICIENT TO IMPART SIGNIFICANT FLAME RETARDENCY TO SAID COMPOSITION.
 2. A composition according to claim 1, in which the inorganic compound is a natural mineral comprising a hydrated salt.
 3. A composition according to claim 2, in which the inorganic compound is colemanite.
 4. A composition according to claim 2, in which the inorganic compound is selected from ulexite and pandermite.
 5. A composition according to claim 1, in which said composition also contains a flame-retarding agent in addition to said compound.
 6. A composition according to claim 5, in which said additional flame-retarding agent is selected from tri-hydrate of alumina and organic flame-retardant compounds containing bromine or chlorine.
 7. A composition according to claim 1, which contains calcium carbonate as a filler.
 8. A composition according to claim 1, which is unfoamed and in which the average grain diameter of said inorganic compOund is about 1 micron.
 9. A composition according to claim 1, which is foamed and in which the inorganic compound has an average grain diameter from 3 to 150 microns.
 10. Carpet and upholstery material, comprising a composition as claimed in claim 1 adhered to the undersurface of said carpet and upholstery material. 